Surgical interventions represent an important stress for the organism. Metabolic parameters can exhibit important changes in a short period of time related to surgery. Differences might occur between normal weight and obese patients. Weight excess represents a risk factor for osteoarthritis.The aim of the study was to assess metabolic parameters before and after total hip and knee replacement in patients with osteoarthritis. The study was performed during 2016-2017 at the Clinic of Orthopedics and Traumatology of the Emergency County Hospital in Tirgu Mures. The study group was divided, based on body mass index values, in normal weight (43 patients) and obese individuals (52 patients). Plasma uric acid level, glycemia and lipid profile (triglycerides, total cholesterol) were determined for each patient before surgery and one day after the intervention, the values being compared. Differences between the metabolic parameters of the two subgroups were also determined. In case of obese individuals, all followed metabolic parameters were significantly different one day after the intervention compared to the values obtained before the surgery: plasma uric acid, cholesterol and triglyceride values decreased, glycemia increased. In the group of normal weight subjects the level of plasma lipids and uric acid differed significantly between the first and second sample, mean values being decreased in the second one. Comparing the two subgroups, significant difference occured regarding plasma glucose levels one day after the intervention, the mean value being higher in case of obese patients, also a higher percentage of hyperuricemia has been found in the group of obese patients. Dynamics of the followed metabolic parameters shows important changes on short term following surgical intervention. Hyperglycemia and hyperuricemia was most common in obese patients, plasma glucose showing increasing tendency after surgery.